I picked up a filter kit for the tranny today and got chatting to the guy at the parts counter. He said the 1980 was a one-off year when it came to transmissions.And he told me the vacuum was set up differently.
Apparently the owner of this parts place has a 1980 and he's tried all sorts of things. He's replaced all the vacuum bits and had a few 2nd opinions and they all seem to agree that 1980 was strange.
Be that as it may I changed my filter today and put in Quaker State semi-synthetic.( They only had two litres of straight synth left or I would have gone that route.)
I pulled out of my driveway and went cruising after I finished.
Instant difference. It shifted the way my wife's car shifts (a 1982).

For the first time it downshifted immediately when I threw the shifter to " S ".
Upshifts were smooth with no flaring.
Kickdown worked correctly.

That was for the first ten minutes.
Then the flaring began again.
I pulled back into the driveway again and saw that I was leaking ATF from the pan. I'd had a funny feeling as I was putting the pan back on; that the gasket ( which seemed slightly undersized as I stretched it over the rim) had slipped out of place as I pushed the pan into position. Yup . . . that'd be it !
I sure wasn't happy about crawling underneath there again, especially since it was now raining.
Pushed the gasket back into place ( more maleable now) and zipped it all up again.
And another test drive. Took it for a long spin this time and once again the symptons worsened the longer I drove. Took it out on the highway and burned up and down a bit. It was definitely better (perhaps 30% ? ) than before the new filter and fluid but I know there's still something very wrong.

Coupla Questions ! ?

Just what exactly happens when you're a quart over on fluid ?
I was over my first trip out of the driveway (misread the quantity in the Haynes :-> ) but didn't sense anything too amiss.
And . .
Why does it shift perfectly sometimes and not others ?


I think this tranny business is a big issue for owners of older diesels and from the searching I've done, it doesn't appear that anyone has yet put together the perfect guide. Though many seem to have come close.

Jim